WO2024105496A1

WO2024105496A1 - Methods and systems to improve light olefin yield and feedstock utilization from c5 raffinate streams

Info

Publication number: WO2024105496A1
Application number: PCT/IB2023/061239
Authority: WO
Inventors: Zeeshan NAWAZ; Deepak PAL; Prasanna Kumar Pathath; Shehzada Khurram
Original assignee: Sabic Global Technologies B.V.
Priority date: 2022-11-15
Filing date: 2023-11-07
Publication date: 2024-05-23

Abstract

Systems and methods for producing light olefins from a natural gas liquid (NGL) or other C5 stream are provided. The method may include supplying a NGL or other C5 stream to a reverse isomerization unit to produce a n-pentane enriched NGL stream and supplying the n- pentane enriched NGL stream to a liquid furnace to produce a pyrolyzed product stream. The method may also include separating the C2 hydrocarbons, the C3 hydrocarbons, the C4 hydrocarbons, the C5 hydrocarbons, and the C6+ hydrocarbons in the pyrolyzed product stream in a separation train and supplying the separated C5 hydrocarbons, or a portion thereof, to a hydrogenation reactor to produce a saturated C5 hydrocarbon stream, followed by recycling the saturated C5 hydrocarbon stream to the reverse isomerization unit.

Description

METHODS AND SYSTEMS TO IMPROVE LIGHT OLEFIN YIELD AND FEEDSTOCK UTILIZATION FROM C5 RAFFINATE STREAMS

TECHNICAL FIELD

[0001] The present disclosure generally relates to systems and methods for increasing light olefin yield and feedstock utilization from natural gas liquids (NGLs) or other C5 streams. More specifically, the present disclosure relates to, among other embodiments, systems and methods for improving ethylene production from NGL feed streams by hydrogenating C5 raffinate streams followed by recycling the saturated C5 raffinate streams to a reverse isomerization reactor to increase the n-C5 feed to furnaces. Hydrogenation can be performed independently or together with a C4 stream.

BACKGROUND

[0002] Ethylene is a desirable industrial compound having a worldwide production greater than that of any other organic compound. Accordingly, ethylene is widely used in the chemical industry, particularly as a feedstock for the production of polyethylene. In addition to other production methods, ethylene may be generated by the pyrolysis of natural gas liquids (NGLs) and/or other C5 streams in liquid furnaces or crackers. The major component of NGLs is mixed pentanes, typically around 50% n-C5 and 43% i-C5, with specific compositions that vary from well to well. Pyrolysis liquid furnaces may be used to crack NGL feedstocks to high value olefins, such as ethylene, propylene, benzene, butadiene, and C5 raffinate. Particularly desirable are lighter olefins which are in greater demand, therefore enhancement of light olefin yield from pyrolysis liquid furnaces enhances the overall profitability of the process. In recent years, the modern chemical industry has been focused on minimizing carbon loss and maximizing productivity in an energy sustainable matter. Accordingly, methods and systems capable of increasing the efficiency of light olefin production, particularly ethylene production, and improving feedstock utilization of NGL-derived streams is desirable.

SUMMARY

[0003] To address these shortcomings in the art, Applicant has developed systems and methods for increasing light olefin yields from pyrolysis of NGL streams or other C5 streams in liquid furnaces by upgrading the feedstock before injection into the liquid furnace, according to the exemplary embodiments disclosed herein. In particular, among other exemplary embodiments, Applicant has developed systems and methods for downstream recycling or pre-processing of NGL hydrocarbon feedstocks using one or more hydrogenation reactors, that perform independently or together with a C4 stream, and reverse isomerization reactors to provide a n-C5 rich feedstock stream to pyrolysis furnaces, thereby enhancing the overall productivity of light olefins, particularly ethylene.

[0004] Systems and methods for the producing light olefins from a natural gas liquid (NGL) stream are provided. In certain embodiments, the method for producing light olefins from a NGL stream may comprise: supplying a natural gas liquid (NGL) stream to a reverse isomerization unit to produce a n-pentane enriched NGL stream; supplying the n-pentane enriched NGL stream to a liquid furnace or one or more pyrolysis furnaces to produce a pyrolyzed product stream, the pyrolyzed product stream comprising C2 hydrocarbons, C3 hydrocarbons, C4 hydrocarbons, C5 hydrocarbons, and C6+ hydrocarbons; separating the C2 hydrocarbons, the C3 hydrocarbons, the C4 hydrocarbons, the C5 hydrocarbons, and the C6+ hydrocarbons in the pyrolyzed product stream in a separation train; supplying the separated C5 hydrocarbons, or a portion thereof, to a first hydrogenation reactor to produce a saturated or hydrogenated C5 hydrocarbon stream; recycling the saturated or hydrogenated C5 hydrocarbon stream to the reverse isomerization unit. [0005] In some embodiments of the method, recycling the saturated or hydrogenated C5 hydrocarbon stream to the reverse isomerization unit increases light olefin yield, particularly ethylene and/or propylene yield at the liquid furnace or one or more liquid furnaces. In some embodiments, the NGL stream may be formed from the combination of a fresh natural gas liquid feed and the saturated or hydrogenated C5 hydrocarbon stream produced at the first hydrogenation reactor. In some embodiments of the method, the method may also include supplying the separated C4 hydrocarbons, or a portion thereof, to a second hydrogenation reactor to produce a saturated or hydrogenated C4 hydrocarbon stream and recycling the saturated or hydrogenated C4 hydrocarbon stream to the reverse isomerization unit.

[0006] In some embodiments, the method may further include supplying the separated C4 hydrocarbons, or a portion thereof, to the first hydrogenation reactor to produce a combined saturated or hydrogenated C4 hydrocarbon and saturated or hydrogenated C5 hydrocarbon stream. In some embodiments, the method may further include recycling the combined saturated or hydrogenated C4 and C5 hydrocarbon stream to the reverse isomerization unit. In some embodiments, the NGL stream may be formed from the combination of a fresh natural gas liquid feed and the combined saturated or hydrogenated C4 and C5 hydrocarbon stream produced at the first hydrogenation reactor. In some embodiments of the method, the NGL stream may be formed from the combination of a fresh natural gas liquid feed, the saturated or hydrogenated C5 hydrocarbon stream produced at the first hydrogenation reactor, and the saturated or hydrogenated C4 hydrocarbon stream produced at the second hydrogenation reactor.

[0007] In some embodiments, the method may further include supplying the C4 hydrocarbons separated from the pyro lyzed product stream to a butadiene and but-l-ene processing unit to produce a butadiene stream, a butene- 1 stream, and a C4 raffinate stream; supplying the C4 raffinate stream to the first hydrogenation reactor or the second hydrogenation reactor to produce a saturated or hydrogenated C4 hydrocarbon stream; and supplying the saturated or hydrogenated C4 hydrocarbon stream to the reverse isomerization unit. In some embodiments, the method may further include separating, at a debutanizer unit, C4 hydrocarbons from the pyrolyzed product stream, or a portion thereof, to produce a separated C4 hydrocarbon stream; and supplying the separated C4 hydrocarbon stream to the butadiene and but-l-ene processing unit.

[0008] In some embodiments, the method may further include supplying the pyrolyzed product stream to a product recovery section of the separation train operable to separate propylene and ethylene, and/or C2 and C3 hydrocarbons, from the pyrolyzed product stream to produce a C4+ hydrocarbon stream; supplying the C4+ hydrocarbon stream to a debutanizer to produce a separated C4 hydrocarbon stream and a C5+ hydrocarbon stream; supplying the C5+ hydrocarbon stream to a depentanizer to produce a separated C5 hydrocarbon stream (i.e., a C5 raffinate stream) and a C6+ hydrocarbon stream; and supplying the separated C5 hydrocarbon stream to the first hydrogenation reactor. In some embodiments, the method may further include supplying the C5+ hydrocarbon stream or the separated C5 hydrocarbon stream to a gas hydro treatment reactor to prior to supplying the C5 hydrocarbon stream to the first hydrogenation reactor. In some embodiments, the reverse isomerization unit is operated at a temperature of from about 240°C to about 440°C and at a pressure of from about 15 bar to about 30 bar.

[0009] The present disclosure also provides a method for producing light olefins from a NGL stream that may comprise: hydrogenating a recycled C5 stream to produce a saturated recycled C5 stream, the recycled C5 stream derived from the pyrolysis of a natural gas liquid stream; isomerizing the hydrogenated recycled C5 stream and iso-C5 from a fresh natural gas liquid stream to produce an isomerized hydrocarbon stream; and pyrolyzing the isomerized hydrocarbon stream to produce one or more light olefins and one or more additional pyrolyzed products. In some embodiments, the method may also include hydrogenating a recycled C4 stream and a recycled C5 stream to produce a hydrogenated recycled mixed C4 and C5 stream, the recycled C4 stream and the recycled C5 stream derived from the pyrolysis of a natural gas liquid stream; isomerizing the hydrogenated recycled mixed C4 and C5 stream and a fresh natural gas liquid stream to produce an isomerized hydrocarbon stream; and pyrolyzing the isomerized hydrocarbon stream to produce one or more light olefins and one or more pyrolyzed products.

[0010] In some embodiments, the recycled C5 stream may be separated from the one or more pyrolyzed products. In some embodiments, the recycled C4 stream may be separated from the one or more pyrolyzed products. In some embodiments, the method may also include separating the one or more light olefins from the one or more pyrolyzed products. In some embodiments, the method may also include feeding the one or more additional pyrolyzed products to a debutanizer to produce the recycled C4 stream and a debutanized hydrocarbon stream. In some embodiments, the method may also include feeding the debutanized hydrocarbon stream to a gas hydrotreatment (GHT) reactor to produce a treated debutanized hydrocarbon stream; and feeding the treated debutanized hydrocarbon stream to a depentanizer to produce the recycled C5 stream. In some embodiments, the recycled C5 stream is a pentene-rich stream and the hydrogenated recycled C5 stream is a pentane-rich stream. In some embodiments, the recycled C4 stream is a butene-rich stream and the hydrogenated recycled mixed C4 and C5 stream is a pentane-rich and butane-rich stream.

[0011] The present disclosure provides a system for producing light olefins from a natural gas liquid stream. The system may include: a reverse isomerization unit operable to receive a natural gas liquid (NGL) stream, the reverse isomerization unit further operable to isomerize the NGL stream to produce a n-pentane enriched NGL stream; a liquid furnace or one or more pyrolysis furnaces operable to receive the n-pentane enriched NGL stream, the liquid furnace or the one or more pyrolysis furnaces further operable to pyrolyze the n-pentane enriched NGL stream to produce a pyrolyzed product stream, the pyrolyzed product stream comprising C2 hydrocarbons, C3 hydrocarbons, C4 hydrocarbons, C5 hydrocarbons, and C6+ hydrocarbons; a separation train operable to separate the C2 hydrocarbons, the C3 hydrocarbons, the C4 hydrocarbons, the C5 hydrocarbons, and the C6+ hydrocarbons in the pyrolyzed product stream; and a first hydrogenation reactor operable to receive the separated C5 hydrocarbons, or a portion thereof, the first hydrogenation reactor further operable to hydrogenate the separated C5 hydrocarbons, or a portion thereof, to produce a saturated or hydrogenated C5 hydrocarbon stream; the reverse isomerization unit further operable to receive the saturated or hydrogenated C5 hydrocarbon stream.

[0012] In some embodiments of the system, recycling the saturated or hydrogenated C5 hydrocarbon stream to the reverse isomerization unit increases light olefin yield, particularly ethylene and/or propylene yield, at the liquid furnace. In some embodiments of the system, the NGL stream may be formed from the combination of a fresh natural gas liquid feed and the saturated or hydrogenated C5 hydrocarbon stream produced at the first hydrogenation reactor. In some embodiments, the system may further include a second hydrogenation reactor operable to receive the separated C4 hydrocarbons, or a portion thereof. The second hydrogenation reactor may be further operable to hydrogenate the separated C4 hydrocarbons, or a portion thereof, to produce a saturated or hydrogenated C4 hydrocarbon stream. The reverse isomerization unit may be operable to receive the saturated or hydrogenated C4 hydrocarbon stream produced by the second hydrogenation reactor. [0013] In some embodiments of the system, the first hydrogenation reactor may be configured to receive the separated C4 hydrocarbons, or a portion thereof. The first hydrogenation reactor may be further operable to hydrogenate the separated C4 hydrocarbons, or a portion thereof, to produce a combined saturated or hydrogenated C4 hydrocarbon and a saturated or hydrogenated C5 hydrocarbon stream. The reverse isomerization unit may be configured to receive the combined saturated or hydrogenated C4 and C5 hydrocarbon stream. In some embodiments of the system, the NGL stream may be formed from the combination of a fresh natural gas liquid feed and the combined saturated or hydrogenated C4 and C5 hydrocarbon stream produced at the first hydrogenation reactor. In some embodiments of the system, the NGL stream may be formed from the combination of a fresh natural gas liquid feed, the saturated or hydrogenated C5 hydrocarbon stream produced at the first hydrogenation reactor, and the saturated or hydrogenated C4 hydrocarbon stream produced at the second hydrogenation reactor.

[0014] In some embodiments, the system may also a butadiene and but-l-ene processing unit operable to receive the C4 hydrocarbons separated from the pyrolyzed product stream. The butadiene and but-l-ene processing unit may be further operable to produce a butadiene stream, a butene- 1 stream, and a C4 raffinate stream. The first hydrogenation reactor or the second hydrogenation reactor may be operable to receive the C4 raffinate stream and produce a saturated (hydrogenated) C4 hydrocarbon stream. The reverse isomerization unit may be operable to receive the saturated (hydrogenated) C4 hydrocarbon stream produced by the first or second hydrogenation reactors.

[0015] In some embodiments, the system may further include a debutanizer unit operable to receive the pyrolyzed product stream, or a portion thereof. The debutanizer unit may be further operable to separate C4 hydrocarbons from the pyrolyzed product stream to produce a separated C4 hydrocarbon stream. The butadiene and but-l-ene processing unit may also be operable to receive the separated C4 hydrocarbon stream produced by the debutanizer unit.

[0016] In some embodiments, the separation train of the system may include a product recovery section configured to receive the pyrolyzed product stream produced by the liquid furnace, the product recovery section further configured to separate propylene and ethylene (C2 and C3 hydrocarbons) from the pyrolyzed product stream to produce a C4+ hydrocarbon stream; a debutanizer configured to receive the C4+ hydrocarbon stream produced by the product recovery section, the debutanizer further configured to debutanize the C4+ hydrocarbon stream to produce a separated C4 hydrocarbon stream and a C5+ hydrocarbon stream; and a depentanizer configured to receive the C5+ hydrocarbon stream produced by the debutanizer, the depentanizer further configured to depentenize the C5+ hydrocarbon stream to produce a separated C5 hydrocarbon (raffinate) stream and a C6+ hydrocarbon stream. In such embodiments, the first hydrogenation reactor may be operable to receive the separated C5 hydrocarbon stream produced by the depentanizer.

[0017] In some embodiments of the system, the product recovery section may include a deethanizer operable to receive the pyrolyzed product stream, or a portion thereof, and produce a separated C2 hydrocarbon stream; and a depropanizer operable to receive the pyrolyzed products stream, or a portion thereof, and produce a separated C3 hydrocarbon stream. The separated C2 hydrocarbon stream may comprise ethylene and the separated C3 hydrocarbon stream may comprise propylene. The de-ethanizer may be configured to produce a C3+ hydrocarbon stream and the depropanizer may be configured to receive the C3+ hydrocarbon stream produced by the de-ethanizer and produce a separated C3 hydrocarbon stream and a C4+ hydrocarbon stream. In some embodiments, the system may further include a gas hydro treatment reactor configured to receive the C5+ hydrocarbon stream produced by the debutanizer or the separated C5 hydrocarbon stream (i.e., the C5 raffinate stream) produced by the depentanizer prior to supplying the C5 hydrocarbon stream to the first hydrogenation reactor. In some embodiments of the system, the reverse isomerization unit is operated at a temperature of from about 240°C to about 440°C and at a pressure of from about 15 bar to about 30 bar.

[0018] The present disclosure also provides a system for producing light olefins from a NGL stream that may comprise: a hydrogenation reactor operable to receive a recycled C5 stream derived from the pyrolysis of a natural gas liquid stream and operable to hydrogenize the recycled C5 stream to produce a hydrogenated recycled C5 stream; a reverse isomerization reactor operable to receive a fresh natural gas liquid stream and the hydrogenated recycled C5 stream, the reverse isomerization reactor further operable to isomerize the combined fresh natural gas liquid stream and the hydrogenated recycled C5 stream to produce an isomerized hydrocarbon stream; and one or more pyrolysis furnaces operable to receive the isomerized hydrocarbon stream and pyrolyze the isomerized hydrocarbon stream to produce one or more light olefins and one or more pyrolyzed products.

[0019] In some embodiments of the system, the hydrogenation reactor may be further operable to receive a recycled C4 stream derived from the pyrolysis of a natural gas liquid stream and hydrogenize the combined recycled C4 and C5 streams to produce a hydrogenated recycled mixed C4 and C5 stream. The reverse isomerization reactor may be operable to receive the fresh natural gas liquid stream and the hydrogenated recycled mixed C4 and C5 stream. The reverse isomerization reactor may be further operable to isomerize the combined fresh natural gas liquid stream and the hydrogenated recycled mixed C4 and C5 stream to produce the isomerized hydrocarbon stream. In some embodiments, the system may further include one or more separators operable to separate the one or more light olefins from the one or more pyrolyzed products. In some embodiments, the system may further include a debutanizer operable to receive the one or more additional pyrolyzed products and produce the recycled C4 stream and a debutanized hydrocarbon stream.

[0020] In some embodiments, the system may further include a gas hydro treatment (GHT) reactor operable to receive the debutanized hydrocarbon stream from the debutanizer and produce a treated debutanized hydrocarbon stream. In some embodiments, the system may further include a depentanizer operable to receive the treated debutanized hydrocarbon stream and produce the recycled C5 stream and a C6-C8 stream. In some embodiments, the recycled C5 stream may be a pentene-rich stream and the hydrogenated recycled C5 stream may be a pentane-rich stream. In some embodiments of the system, the recycled C4 stream may be a butene-rich stream. In some embodiments of the system, the hydrogenated recycled mixed C4 and C5 stream may be a pentane- rich and butane-rich stream.

[0021] Still other aspects and advantages of these exemplary embodiments and other embodiments, are discussed in detail herein. Moreover, it is to be understood that both the foregoing information and the following detailed description provide merely illustrative examples of various aspects and embodiments, and are intended to provide an overview or framework for understanding the nature and character of the claimed aspects and embodiments. Accordingly, these and other objects, along with advantages and features of the present disclosure, will become apparent through reference to the following description and the accompanying drawings. Furthermore, it is to be understood that the features of the various embodiments described herein are not mutually exclusive and may exist in various combinations and permutations.

BRIEF DESCRIPTION OF THE DRAWINGS [0022] The accompanying drawings, which are included to provide a further understanding of the embodiments of the present disclosure, are incorporated in and constitute a part of this specification, illustrate embodiments of the present disclosure, and together with the detailed description, serve to explain principles of the embodiments discussed herein. No attempt is made to show structural details of this disclosure in more detail than may be necessary for a fundamental understanding of the embodiments discussed herein and the various ways in which they may be practiced. According to common practice, the various features of the drawings discussed below are not necessarily drawn to scale. Dimensions of various features and elements in the drawings may be expanded or reduced to more clearly illustrate embodiments of the disclosure.

[0023] FIG. 1 is a graphical representation of a system and method for producing light olefins from a NGL stream that includes feeding unhydrogenated C4 and C5 hydrocarbon streams separated from a pyrolysis product stream to a single hydrogenation reactor, followed by recycling the hydrogenated C4/C5 hydrocarbon stream to a reverse isomerization reactor, according to an exemplary embodiment of the present disclosure.

[0024] FIG. 2 is a graphical representation of a system and method for producing light olefins from a NGL stream that includes feeding an unhydrogenated C5 hydrocarbon stream separated from a pyrolysis product stream to a hydrogenation reactor, followed by recycling the hydrogenated C5 hydrocarbon stream to a reverse isomerization reactor, according to an exemplary embodiment of the present disclosure.

DETAILED DESCRIPTION

[0025] The present disclosure describes various embodiments related to processes, methods, and systems for integrating petrochemical and refinery operations. Further embodiments may be described and disclosed. [0026] In the following description, numerous details are set forth in order to provide a thorough understanding of the various embodiments. In other instances, well-known processes, devices, and systems may not have been described in particular detail in order not to unnecessarily obscure the various embodiments. Additionally, illustrations of the various embodiments may omit certain features or details in order to not obscure the various embodiments.

[0027] The description may use the phrases “in some embodiments,” “in various embodiments,” “in an embodiment,” or “in embodiments,” which may each refer to one or more of the same or different embodiments. Furthermore, the terms “comprising,” “including,” “having,” and the like, as used with respect to embodiments of the present disclosure, are synonymous.

[0028] The term “about” is defined as being close to as understood by one of ordinary skill in the art. In one non-limiting embodiment, the terms are defined to be within 10%, preferably within 5%, more preferably within 1%, and most preferably within 0.5%.

[0029] The terms “reducing,” “reduced,” or any variation thereof, when used in the claims and/or the specification includes any measurable decrease or complete inhibition to achieve a desired result.

[0030] The use of the words “a” or “an” when used in conjunction with any of the terms “comprising,” “including,” “containing,” or “having,” in the claims or the specification may mean “one,” but it is also consistent with the meaning of “one or more,” “at least one,” and “one or more than one.” The terms “wt.%”, “vol.%”, or “mol.%” refers to a weight, volume, or molar percentage of a component, respectively, based on the total weight, the total volume of material, or total moles, that includes the component. In a non-limiting example, 10 grams of component in 100 grams of the material is 10 wt.% of component. [0031] The words “comprising” (and any form of comprising, such as “comprise” and “comprises”), “having” (and any form of having, such as “have” and “has”), “including” (and any form of including, such as “includes” and “include”) or “containing” (and any form of containing, such as “contains” and “contain”) are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.

[0032] Disclosed here are systems and methods for increasing light olefin yields from the pyrolysis of NGL streams in liquid furnaces by upgrading the feedstock before injection into the liquid furnace. In particular, prior to being fed to one or more pyrolysis furnaces, a fresh NGL stream may be mixed or combined with a n-C5 rich feedstock stream produced by one or more hydrogenation reactors from a recycled C5 hydrocarbon stream separated from a pyrolyzed product stream.

[0033] Pre-processing of NGL hydrocarbon feedstocks using one or more hydrogenation reactors and reverse isomerization reactors provides a n-C5 rich feedstock stream to pyrolysis furnaces, thereby enhancing the overall productivity of light olefins, particularly ethylene.

[0034] FIG. 1 is a graphical representation of an exemplary system 100 and method for producing ethylene and other light olefins from a natural gas liquid feed stream 105 that includes feeding unhydrogenated C4 and C5 hydrocarbon streams 178, 185 separated from a pyrolysis product stream 125, by a separation train 128, to a single hydrogenation reactor 190, followed by recycling the hydrogenated C4/C5 hydrocarbon stream 195 to a reverse isomerization reactor 110, according to an exemplary embodiment of the present disclosure. As depicted in FIG. 1, system 100 may include one or more reverse isomerization reactors, such as reverse isomerization reactor 110. Reverse isomerization reactor 110 may be operable to receive a natural gas liquid (NGL) stream 101, such as fresh NGL feed stream 105 and isomerize the NGL feed stream 101 to produce an isomerized hydrocarbon stream 115 or n-pentane enriched NGL stream 115.

[0035] As depicted in FIG. 1, the reverse isomerization reactor 110 may be fluidly coupled with one or more pyrolysis furnaces, such as liquid furnace 120. Liquid furnace 120 may be operable to receive the isomerized hydrocarbon stream 115 or the n-pentane enriched NGL stream 115 produced by the reverse isomerization reactor 110. Liquid furnace 120 may also be operable to pyrolyze the isomerized hydrocarbon stream 115 or the n-pentane enriched NGL stream 115 to produce a pyrolyzed product stream 125. The pyrolyzed product stream 125 may comprise C2 hydrocarbons, C3 hydrocarbons, C4 hydrocarbons, C5 hydrocarbons, and C6+ hydrocarbons, among other hydrocarbons and chemical components. As used herein, the term “C6+ hydrocarbons,” refers to hydrocarbons having six (6) or more carbon atoms. Similar terms, such as “C3+ hydrocarbons,” “C4+ hydrocarbons,” and “C5+ hydrocarbons,” also refers to hydrocarbons having three (3) or more carbon atoms, four (4) or more carbons atoms, and five (5) or more carbon atoms, respectively.

[0036] System 100 may further include a separation train 128 operable to separate the C2 hydrocarbons, the C3 hydrocarbons, the C4 hydrocarbons, the C5 hydrocarbons, and the C6+ hydrocarbons in the pyrolyzed product stream 125. Accordingly, separation train 128 is fluidly coupled to pyrolysis furnace 120 and operable to receive the pyrolyzed product stream 125 produced by pyrolysis furnace 120. As depicted in FIG. 1, the separation train 128 in system 100 may include a product separation section 130, a debutanizer 140, a depentanizer 180, a butadiene and but-l-ene processing unit 170, and a stabilizer/deoctanizer 160. The product separation section 130 of separation train 128 may be fluidly coupled to the liquid furnace 120 and operable to receive the pyrolyzed product stream 125 produced by the liquid furnace 120. Product separation section 130 may include components operable to separate light olefin products produced by pyrolysis in the liquid furnace 120, such as ethylene and propylene, as well as other C2 and C3 hydrocarbons. Accordingly, product separation section 130 may include a de-ethanizer and a depropanizer. After product separation, the resultant C4+ hydrocarbon stream 135 (e.g., depropanizer bottoms stream) may be supplied to debutanizer 140.

[0037] As depicted in FIG. 1, system 100 may include debutanizer 140 fluidly coupled with product separation section 130 and operable to receive the C4+ hydrocarbon stream 135 produced by product separation section 130. Debutanizer 140 may be operable to separate C4 hydrocarbons from the C4+ hydrocarbon stream 135 to produce a separated C4 hydrocarbon stream 145 and a C5+ hydrocarbon stream 146. Separation train 128 of system 100 may further include a butadiene and but-l-ene processing unit 170 fluidly coupled to debutanizer 140 and operable to receive separated C4 hydrocarbon stream 145. Butadiene and but-l-ene processing unit 170 is further operable to process the separated C4 hydrocarbon stream 145 to produce a butadiene product stream 171, a butene-1 product stream 172, raffinate to dehydrogenation or other use 173, and C4 raffinate stream 175. Butadiene and but-l-ene processing unit 170 may be fluidly coupled to unhydrogenated mixC4 sphere 177 and C4/C5 hydrogenation reactor 190 or first hydrogenation reactor 190.

[0038] System 100 may also include a gas hydrotreatment (GHT) reactor 150 fluidly coupled with debutanizer 140 such that the GHT reactor 150 is operable to receive the C5+ hydrocarbon stream 146 produced by debutanizer 140. GHT reactor 150 is operable to hydrotreat the C5+ hydrocarbon stream 146 and produce hydrotreated C5+ hydrocarbon stream 155. As depicted in FIG. 1, GHT reactor 150 is fluidly coupled with stabilizer/deoctanizer 160. Stabilizer/deoctanizer 160 is operable to receive the hydrotreated C5+ hydrocarbon stream 155 produced by GHT reactor 150 and produce fuel gas stream 163, C9+ residue stream 161, wash oil stream 162, and residual C5+ hydrocarbon stream 165.

[0039] Separation train 128 of system 100 further includes depentanizer 180 fluidly coupled with stabilizer/deoctanizer 160 and operable to receive residual C5+ hydrocarbon stream 165 produced by stabilizer/deoctanizer 160. Depentanizer 180 may be operable to separate C5 hydrocarbons from the residual C5+ hydrocarbon stream 165 to produce a separated C5 hydrocarbon stream 185 or C5 raffinate stream 185 and a C6+ hydrocarbon stream 186. The separated C5 hydrocarbon stream or C5 raffinate stream 185 may be supplied to the C4/C5 hydrogenation reactor 190 in the form of combined C4/C5 raffinate stream 178 or combined separated C4/C5 stream 178.

[0040] C4/C5 hydrogenation reactor 190 may be operable to receive C4 raffinate stream 175 or separated C4 stream 178 from unhydrogenated mixC4 sphere 177 as well as separated C5 hydrocarbon stream or C5 raffinate stream 185 in the form of combined separated C4/C5 stream 178. C4/C5 hydrogenation reactor 190 is further operable to hydrogenate or saturate the combined separated C4/C5 stream 178 to produce a saturated or hydrogenated C4/C5 hydrocarbon stream 195. C4/C5 hydrogenation reactor 190 is fluidly coupled to reverse isomerization reactor 110 such that combined saturated/hydrogenated C4/C5 hydrocarbon stream 195 may be supplied to reverse isomerization reactor 110 as either a separate feed stream to reverse isomerization reactor 110 or as part of a combined stream with fresh NGL feed stream 105 in the form of NGL stream 101.

[0041] While FIG. 1 depicts a single C4/C5 hydrogenation reactor 190, in other embodiments of system 100, C4/C5 hydrogenation reactor 190 may be replaced by any number of hydrogenation reactors configured to receive unhydrogenated C4 and C5 streams separated from pyrolyzed product stream 125. In some embodiments, the single C4/C5 hydrogenation reactor 190 may be replaced by a first hydrogenation reactor operable to receive and hydrogenate/ saturate a separated C5 hydrocarbon stream or C5 raffinate stream and a second hydrogenation reactor operable to receive and hydrogenate/saturate a separated C4 hydrocarbon stream or C4 raffinate stream. The output streams of the first and second hydrogenation reactors may be combined to form saturated/hydrogenated C4/C5 hydrocarbon stream 195 and supplied to reverse isomerization reactor 110 either separately or as a combined feed stream with fresh NGL feed stream 105 to form NGL feed 101.

[0042] FIG. 2 is a graphical representation of an exemplary system 200 and method for producing ethylene and other light olefins from a natural gas liquid feed stream 205 that includes feeding unhydrogenated C5 hydrocarbon stream 285 separated from a pyrolysis product stream 225 by a separation train 228 to a C5 hydrogenation reactor 290, followed by recycling the hydrogenated/saturated C5 hydrocarbon stream 295 to a reverse isomerization reactor 210, according to an exemplary embodiment of the present disclosure. As depicted in FIG. 2, system 200 may include one or more reverse isomerization reactors, such as reverse isomerization reactor 210. Reverse isomerization reactor 210 may be operable to receive a natural gas liquid (NGL) stream 201, such as fresh NGL feed stream 205 and isomerize the NGL feed stream 201 to produce an isomerized hydrocarbon stream 215 or n-pentane enriched NGL stream 215.

[0043] As depicted in FIG. 2, the reverse isomerization reactor 210 may be fluidly coupled with one or more pyrolysis furnaces, such as liquid furnace 220. Liquid furnace 220 may be operable to receive the isomerized hydrocarbon stream 215 or the n-pentane enriched NGL stream 215 produced by the reverse isomerization reactor 210. Liquid furnace 220 may also be operable to pyrolyze the isomerized hydrocarbon stream 215 or the n-pentane enriched NGL stream 215 to produce a pyrolyzed product stream 225. The pyrolyzed product stream 225 may comprise C2 hydrocarbons, C3 hydrocarbons, C4 hydrocarbons, C5 hydrocarbons, and C6+ hydrocarbons, among other hydrocarbons and chemical components.

[0044] System 200 may further include a separation train 228 operable to separate the C2 hydrocarbons, the C3 hydrocarbons, the C4 hydrocarbons, the C5 hydrocarbons, and the C6+ hydrocarbons in the pyrolyzed product stream 225. Accordingly, separation train 228 is fluidly coupled to pyrolysis furnace 220 and operable to receive the pyrolyzed product stream 225 produced by pyrolysis furnace 220. As depicted in FIG. 2, the separation train 228 in system 200 may include a product separation section 230, a debutanizer 240, a depentanizer 280, and a stabilizer/deoctanizer 260. The product separation section 230 of separation train 228 may be fluidly coupled to the liquid furnace 220 and operable to receive the pyrolyzed product stream 225 produced by the liquid furnace 220. Product separation section 230 may include components operable to separate light olefin products produced by pyrolysis in the liquid furnace 220, such as ethylene and propylene, as well as other C2 and C3 hydrocarbons. Accordingly, product separation section 230 may include a de-ethanizer and a depropanizer. After product separation, the resultant C4+ hydrocarbon stream 235 (e.g., depropanizer bottoms stream) may be supplied to debutanizer 240.

[0045] As depicted in FIG. 2, system 200 may include debutanizer 240 fluidly coupled with product separation section 230 and operable to receive the C4+ hydrocarbon stream 235 produced by product separation section 230. Debutanizer 240 may be operable to separate C4 hydrocarbons from the C4+ hydrocarbon stream 235 to produce a separated C4 hydrocarbon stream 245 and a C5+ hydrocarbon stream 246. System 200 may also include a gas hydrotreatment (GHT) reactor 250 fluidly coupled with debutanizer 240 such that the GHT reactor 250 is operable to receive the C5+ hydrocarbon stream 246 produced by debutanizer 240. GHT reactor 250 is operable to hydrotreat the C5+ hydrocarbon stream 246 and produce hydrotreated C5+ hydrocarbon stream 255. As depicted in FIG. 2, GHT reactor 250 is fluidly coupled with stabilizer/deoctanizer 260. Stabilizer/deoctanizer 260 is operable to receive the hydrotreated C5+ hydrocarbon stream 255 produced by GHT reactor 250 and produce fuel gas stream 263, C9+ residue stream 261, wash oil stream 262, and residual C5+ hydrocarbon stream 265.

[0046] Separation train 228 of system 200 further includes depentanizer 280 fluidly coupled with stabilizer/deoctanizer 260 and operable to receive residual C5+ hydrocarbon stream 265 produced by stabilizer/deoctanizer 260. Depentanizer 280 may be operable to separate C5 hydrocarbons from the residual C5+ hydrocarbon stream 265 to produce a separated C5 hydrocarbon stream 285 or C5 raffinate stream 285 and a C6+ hydrocarbon stream 286. The separated C5 hydrocarbon stream or C5 raffinate stream 285 may be supplied to the C5 hydrogenation reactor 290 (e.g., first hydrogenation reactor 290).

[0047] C5 hydrogenation reactor 290 may be operable to receive the separated C5 hydrocarbon stream or C5 raffinate stream 285 produced by depentanizer 280 and hydrogenate or saturate the separated C5 hydrocarbon stream or C5 raffinate stream 285 to produce a saturated or hydrogenated C5 hydrocarbon stream 295. The C5 hydrogenation reactor 290 is fluidly coupled to reverse isomerization reactor 210 such that the saturated/hydrogenated C5 hydrocarbon stream 295 may be supplied to reverse isomerization reactor 210 as either a separate feed stream to reverse isomerization reactor 210 or as part of a combined stream with fresh NGL feed 205 in the form of NGL stream 201.

EXAMPLES [0048] The examples provided below illustrate selected aspects of the various methods and systems for producing light olefins from a NGL stream and do no limit the scope of the disclosure in any manner.

Example 1 [0049] Hydrocarbon yields for system 100 depicted in FIG. 1 are shown in Table 1 as determined by simulation. As shown in Table 1, system 100 produced 9.93 tons per hour (T/hr) ethylene and 3.75 T/hr propylene at the furnace outlet from an exemplary NGL fresh feed comprising 9.48 T/hr isopentane and 13.35 T/hr.

Table 1

Example 2

[0050] Hydrocarbon yields for system 200 depicted in FIG. 2 are shown in Table 2 as determined by simulation. As shown in Table 2, system 200 produced 11.99 tons per hour (T/hr) ethylene and 4.49 T/hr propylene at the furnace outlet from a NGL fresh feed comprising 9.48 T/hr isopentane and 13.35 T/hr. Accordingly, C5 hydrogenation of a recycled C5 hydrocarbon stream separated from a pyrolyzed product stream, according to the system and method depicted in FIG.

2, resulted in a 20% increase in ethylene yield and propylene yield as compared to the C4/C5 hydrogenation system 100 depicted in FIG. 1 (Example 1). Table 2

[0051] When ranges are disclosed herein, ranges from any lower limit may be combined with any upper limit to recite a range not explicitly recited, as well as, ranges from any lower limit may be combined with any other lower limit to recite a range not explicitly recited, in the same way, ranges from any upper limit may be combined with any other upper limit to recite a range not explicitly recited. Additionally, reference to values stated in ranges includes each and every value within that range, even though not explicitly recited. Thus, every point or individual value may serve as its own lower or upper limit combined with any other point or individual value or any other lower or upper limit, to recite a range not explicitly recited.

[0052] Other objects, features and advantages of the disclosure will become apparent from the foregoing figures, detailed description, and examples. It should be understood, however, that the figures, detailed description, and examples, while indicating specific embodiments of the disclosure, are given by way of illustration only and are not meant to be limiting. In further embodiments, features from specific embodiments may be combined with features from other embodiments. For example, features from one embodiment may be combined with features from any of the other embodiments. In further embodiments, additional features may be added to the specific embodiments described herein.

Claims

Claims What is claimed is:

1. A method for producing light olefins from a natural gas liquid stream, the method comprising: supplying a natural gas liquid (NGL) stream to a reverse isomerization unit to produce a n-pentane enriched NGL stream; supplying the n-pentane enriched NGL stream to a liquid furnace to produce a pyrolyzed product stream, the pyrolyzed product stream comprising C2 hydrocarbons, C3 hydrocarbons, C4 hydrocarbons, C5 hydrocarbons, and C6+ hydrocarbons; separating the C2 hydrocarbons, the C3 hydrocarbons, the C4 hydrocarbons, the C5 hydrocarbons, and the C6+ hydrocarbons in the pyrolyzed product stream in a separation train; supplying the separated C5 hydrocarbons, or a portion thereof, to a first hydrogenation reactor to produce a saturated C5 hydrocarbon stream; and recycling the saturated C5 hydrocarbon stream to the reverse isomerization unit.

2. The method according to claim 1, wherein recycling the saturated C5 hydrocarbon stream to the reverse isomerization unit increases an ethylene and/or a propylene yield at the liquid furnace.

3. The method according to claim 1 or claim 2, wherein the NGL stream is formed from the combination of a fresh natural gas liquid feed and the saturated C5 hydrocarbon stream produced at the first hydrogenation reactor.

4. The method according to any one of claims 1-3, further comprising: supplying the separated C4 hydrocarbons, or a portion thereof, to a second hydrogenation reactor to produce a saturated C4 hydrocarbon stream; recycling the saturated C4 hydrocarbon stream to the reverse isomerization unit.

5. The method according to any one of claims 1-3, further comprising: supplying the separated C4 hydrocarbons, or a portion thereof, to the first hydrogenation reactor to produce a combined saturated C4 hydrocarbon and saturated C5 hydrocarbon stream; and recycling the combined saturated C4 and C5 hydrocarbon stream to the reverse isomerization unit.

6. The method according to claim 5, wherein the NGL stream is formed from the combination of a fresh natural gas liquid feed and the combined saturated C4 and C5 hydrocarbon stream produced at the first hydrogenation reactor.

7. The method according to claim 4, wherein the NGL stream is formed from the combination of a fresh natural gas liquid feed, the saturated C5 hydrocarbon stream produced at the first hydrogenation reactor, and the saturated C4 hydrocarbon stream produced at the second hydrogenation reactor.

8. The method according to any one of claims 1-7, further comprising: supplying the C4 hydrocarbons separated from the pyrolyzed product stream to a butadiene and but-l-ene processing unit to produce a butadiene stream, a butene- 1 stream, and a C4 raffinate stream; supplying the C4 raffinate stream to the first hydrogenation reactor or the second hydrogenation reactor to produce a saturated C4 hydrocarbon stream; and supplying the saturated C4 hydrocarbon stream to the reverse isomerization unit.

9. The method according to claim 8, further comprising: separating, at a debutanizer unit, C4 hydrocarbons from the pyrolyzed product stream, or a portion thereof, to produce a separated C4 hydrocarbon stream; and supplying the separated C4 hydrocarbon stream to the butadiene and but-l-ene processing unit.

10. The method according to any one of claims 1-9, further comprising: supplying the pyrolyzed product stream to a product recovery section of the separation train operable to separate propylene and ethylene from the pyrolyzed product stream to produce a C4+ hydrocarbon stream; supplying the C4+ hydrocarbon stream to a debutanizer to produce a separated C4 hydrocarbon stream and a C5+ hydrocarbon stream; supplying the C5+ hydrocarbon stream to a depentanizer to produce a separated C5 hydrocarbon stream and a C6+ hydrocarbon stream; and supplying the separated C5 hydrocarbon stream to the first hydrogenation reactor.

11. The method according to any one of claims 1-10, further comprising: supplying the C5+ hydrocarbon stream or the separated C5 hydrocarbon stream to a gas hydro treatment reactor prior to supplying the C5 hydrocarbon stream to the first hydrogenation reactor.

12. A system for producing light olefins from a natural gas liquid stream, the system comprising: a reverse isomerization unit operable to receive a natural gas liquid (NGL) stream, the reverse isomerization unit further operable to isomerize the NGL stream to produce a n- pentane enriched NGL stream; a liquid furnace operable to receive the n-pentane enriched NGL stream, the liquid furnace further operable to pyrolyze the n-pentane enriched NGL stream to produce a pyrolyzed product stream, the pyrolyzed product stream comprising C2 hydrocarbons, C3 hydrocarbons, C4 hydrocarbons, C5 hydrocarbons, and C6+ hydrocarbons; a separation train operable to separate the C2 hydrocarbons, the C3 hydrocarbons, the C4 hydrocarbons, the C5 hydrocarbons, and the C6+ hydrocarbons in the pyrolyzed product stream; and a first hydrogenation reactor operable to receive the separated C5 hydrocarbons, or a portion thereof, the first hydrogenation reactor further operable to hydrogenate the separated C5 hydrocarbons, or a portion thereof, to produce a saturated C5 hydrocarbon stream; the reverse isomerization unit further operable to receive the saturated C5 hydrocarbon stream.

13. The system according to claim 12, wherein the separation train comprises: a product recovery section configured to receive the pyrolyzed product stream produced by the liquid furnace, the product recovery section further configured to separate propylene and ethylene from the pyrolyzed product stream to produce a C4+ hydrocarbon stream; a debutanizer configured to receive the C4+ hydrocarbon stream produced by the product recovery section, the debutanizer further configured to debutanize the C4+ hydrocarbon stream to produce a separated C4 hydrocarbon stream and a C5+ hydrocarbon stream; and a depentanizer configured to receive the C5+ hydrocarbon stream produced by the debutanizer, the depentanizer further configured to depentenize the C5+ hydrocarbon stream to produce a separated C5 hydrocarbon stream and a C6+ hydrocarbon stream; wherein the first hydrogenation reactor is operable to receive the separated C5 hydrocarbon stream produced by the depentanizer.

14. The system according to claim 12 or claim 13, further comprising: a gas hydro treatment reactor configured to receive the C5+ hydrocarbon stream produced by the debutanizer or the separated C5 hydrocarbon stream produced by the depentanizer prior to supplying the C5 hydrocarbon stream to the first hydrogenation reactor.

15. The system according to claim 12 or claim 13, or claim 14, wherein the reverse isomerization unit is operated at a temperature of from about 240°C to about 440°C and at a pressure of from about 15 bar to about 30 bar.